Inexpensive and compact chemical analysis systems capable of gas discrimination and quantification are highly desirable especially in the context of rapidly developing mobile sensing and monitoring platforms. Similarly there is also a rapidly developing need for point of care devices for bioanalytical detection of markers of health and disease. Such systems can provide vital information for environmental monitoring, breath analysis, health monitoring, and safety & security systems. While significant progress has been made in recent years in the analysis of gas recognition using various types of transducers coated with a variety of receptor materials [1-10] achieving reliable recognition and their quantification continues to remain as a challenge. In this context, the gas discrimination outcomes achieved through exposure of a spatial array of selectively decorated pixels to an analyte mixture can be vastly improved through a simultaneous temporal separation of the gas mixture components through chromatography. Furthermore, ultrasensitive thermal sensors can be configured into biosensors for selective detection of various bioanalytes [11-16]. In spite of several advantages, thermal biosensors have not been able to achieve the same acceptance as other detection approaches largely due to either large volumes of the required samples or due to the performance degradation arising from the extremely fragile construction and cumbersome functionalization approaches suitable for chip scale calorimeters. This proposal aims to address these shortcomings and proposes a novel whispering gallery mode (WGM) resonator based solution for these challenges.
On-Chip Chromatography:
Chromatography offers a simple way to temporally separate the components in an analyte sample and therefore achieve component discrimination. One of the first analytical components developed using microfabrication techniques was the micro gas chromatograph (μGC) on chip [17]. Microfabricated columns of length equal to their commercial counter parts occupy significantly less space, are batch fabricated and thus can be produced very inexpensively [18]. As compared to conventional columns which require large power [19], the small thermal mass of the chip-sized, microfabricated columns allows for rapid heating and cooling at significantly less power [20, 21]. Finally, miniaturized analytical systems benefit from the favorable scaling laws such as increased surface area to volume ratio. However, integrating μGC columns with in-line high-sensitivity detectors for sensing the elution components proved to be very challenging and has compromised their overall performance.